OH End-Capped Silicone as an Effective Nucleating Agent for Polylactide-A Robotizing Method for Evaluating the Mechanical Characteristics of PLA/Silicone Blends.

Current research on materials engineering focuses mainly on bio-based materials. One of the most frequently studied materials in this group is polylactide (PLA), which is a polymer derived from starch. PLA does not have a negative impact on the natural environment and additionally, it possesses properties comparable to those of industrial polymers. The aim of the work was to investigate the potential of organosilicon compounds as modifiers of the mechanical and rheological properties of PLA, as well as to develop a new method for conducting mechanical property tests through innovative high-throughput technologies. Precise dosing methods were utilized to create PLA/silicone polymer blends with varying mass contents, allowing for continuous characterization of the produced blends. To automate bending tests and achieve comprehensive characterization of the blends, a self-created workstation setup has been used. The tensile properties of selected blend compositions were tested, and their ability to withstand dynamic loads was studied. The blends were characterized through various methods, including rheological (MFI), X-ray (XRD), spectroscopic (FTIR), and thermal properties analysis (TG, DSC, HDT), and they were evaluated using microscopic methods (MO, SEM) to examine their structures.

The 3D-Printed (FDM/FFF) Biocomposites Based on Polylactide and Carbonate Lake Sediments-Towards a Circular Economy.

In this study, composites containing polylactide and carbonate lake sediment in concentrations of 2.5, 5, 10, and 15% by weight were prepared by a 3D printing method. The material for 3D printing was obtained by directly diluting the masterbatch on an injection moulder to the desired concentrations, and after granulation, it was extruded into a filament. The material prepared thusly was used to print standardised samples for mechanical testing. To compare the mechanical properties of the composites obtained by 3D printing and injection moulding, two sets of tests were performed, i.e., mechanical tests (tensile strength, flexural strength, and impact strength) and hydrophobic-hydrophilic surface character testing. The degree of composite waste in the 3D printing was also calculated. Mechanical and surface tests were performed for both systems conditioned at room temperature and after accelerated ageing in a weathering chamber. The study showed differences in the properties of composites obtained by 3D printing. Sedimentary fillers improved the hydrophobicity of the systems compared with pure PLA, but it was not a linear relationship. The PLA/CLS sedB composite had higher strength parameters, especially after ageing in a weathering chamber. This is due to its composition, in which, in addition to calcite and silica, there are also aluminosilicates, causing a strengthening of the PLA matrix.

Beeswax as a natural alternative to synthetic waxes for fabrication of PLA/diatomaceous earth composites.

In this study, injection moulding was applied to produce biocomposites consisting of polylactide (PLA) and amorphous diatomaceous earth used as a filler at different concentrations. Natural wax and synthetic wax were added to improve processing properties, comparing the resulting biocomposites. The use of natural beeswax makes the composite environmentally friendly. The prepared composites contained 2.5, 5, 10 and 15% w/w filler. The test samples have been injection moulded. Rheological, mechanical, surface and other properties were assessed for the fabricated composites. The testing has shown that the use of wax additives has a significant influence on the mechanical properties (tensile strength, flexural strength, impact strength) and the hydrophilicity/hydrophobicity of composite surfaces. The addition of natural wax, especially at lower concentration, has a positive effect on the rheological properties of composites (melt flow rate, MFR), flexural modulus and impact strength. Different composite parameters are modified by different wax types so both natural and synthetic waxes, can be used interchangeably, depending on the required final material characteristics.

Aspects and Principles of Material Connections in Restorative Dentistry-A Comprehensive Review.

The combination of two dissimilar materials has always been a serious problem in dentistry. In order to meet this challenge, it is necessary to combine both chemical methods (treatment with silanes, (meth)acrylic functional monomers) and the development of the surface of the joined material in a physical way, e.g., by sandblasting with alumina, alumina with silica, acid etching, the use of lasers and other means. The purpose of this literature review is to present all methods of joining dental composites with other materials such as ceramics, metal, another composite material. This review covers articles published within the period 2012-2022 in journals indexed in the PubMed database, written in English and describing joining different dental materials to each other. All the critical steps of new joint preparation have been addressed, including proper cleaning of the joint surface, the application of appropriate primers capable of forming a chemical bond between ceramics, zirconium oxide or metals and alloys, and finally, the application of new composite materials.

Carbonate Lake Sediments in the Plastics Processing-Preliminary Polylactide Composite Case Study: Mechanical and Structural Properties.

In this study, the influence of carbonate lake sediments (Polylactide/Carbonate Lake Sediments-PLA/CLS) on the mechanical and structural properties of polylactide matrix composites was investigated. Two fractions of sediments originating from 3-8 and 8-12 m were analysed for differences in particle size by distribution (Dynamic Light Scattering-DLS), phase composition (X-ray Diffraction-XRD), the presence of surface functional groups (Fourier Transform-Infrared-FT-IR), and thermal stability (Thermogravimetric Analysis-TGA). Microscopic observations of the composite fractures were also performed. The effect of the precipitate fraction on the mechanical properties of the composites before and after conditioning in the weathering chamber was verified through peel strength, flexural strength, and impact strength tests. A melt flow rate study was performed to evaluate the effect of sediment on the processing properties of the PLA/CLS composite. Hydrophobic-hydrophilic properties were also investigated, and fracture analysis was performed by optical and electron microscopy. The addition of carbon lake sediments to PLA allows for the obtention of composites resistant to environmental factors such as elevated temperature or humidity. Moreover, PLA/CLS composites show a higher flow rate and higher surface hydrophobicity in comparison with unmodified PLA.

Biocomposites Based on Polyamide 11/Diatoms with Different Sized Frustules.

Amorphous diatomite was used as a filler for a thermoplastic polymer of polyamide 11 obtained from natural sources. The diatomite particles of different sizes were previously fractionated by sedimentation to obtain powders with varying particle size distribution, including powders with or without frustule particles, crushed, uncrushed or agglomerated. Biocomposites containing 2.5, 5, 10 and 20% filler were tested for their mechanical properties, including tensile strength, flexural strength and impact strength. In addition, a particle size analysis (by Dynamic Light Scattering, DLS) was performed and the dispersion of the filler in the polymer matrix (Scanning Electron Microscopy, SEM), thermal parameters (Differential Scanning Calorimetry, DSC, and Dynamic Mechanical Analysis, DMA) were determined. Testing showed that biocomposites modified with diatomaceous earth have a higher mechanical strength than the reference system, especially with larger amounts of the filler (10 and 20%), e.g., the tensile strength of pure PA11 is about 46 MPa, while 20OB and 20OF 47.5 and 47 MPa, respectively, while an increase in max. flexural strength and flexural modulus is also observed compared to pure PA11 by a maximum of 63 and 54%, respectively Diatomaceous earth can be obtained in various ways-it is commercially available or it is possible to breed diatoms in laboratory conditions, while the use of commercially available diatomite, which contains diatoms of different sizes, eliminates the possibility of controlling mechanical parameters by filling biocomposites with a filler with the desired particle size distribution, and diatom breeding is not possible on an industrial scale. Our proposed biocomposite based on fractionated diatomaceous earth using a sedimentation process addresses the current need to produce biocomposite materials from natural sources, and moreover, the nature of the process, due to its simplicity, can be successfully used on an industrial scale.

Novel Multifunctional Spherosilicate-Based Coupling Agents for Improved Bond Strength and Quality in Restorative Dentistry.

The aim of this study was to investigate the restorative connections of composite materials after fracture, under controlled conditions of treating the materials with novel, spherosilicate-based (SS) primers bearing both methacryl (MA) and trimethoxysilyl (TMOS) groups. The chemistry of methacrylate group insertion and reactive groups hydrolysis has been studied with the aid of 1H NMR (Nuclear Magnetic Resonance) spectroscopy. The light-cured resin composites were repaired by activating the connection site with the obtained primers and, for comparison, a silane (methacryloxypropyltrimethoxysilane, MATMOS) as a conventional coupling agent bearing the same reactive groups. The resistance of such a joint was tested in a three-point bending test after 24 h and 28 days period of sample conditioning. The effect of bond application was also studied, showing that spherosilicate-based primers may be used more effectively than MATMOS for two-step (primer-composite) restorative process, while for silane, the three-step process with bond application is crucial for satisfactory joint quality. The joint failure mode was determined by microscopic analysis and it was found that SS-4MA-4TMOS and SS-2MA-6TMOS application resulted in mostly composite, and not joint, failure. After 28 days of conditioning, the flexural strength of the joint repaired with SS-4MA-4TMOS was at 94% of the neat, solid material under the same procedure. However, the strength of the neat composite was observed to decline during the conditioning process by ~30%. The joint behavior was explained on the basis of the gradual hydrolysis effect (the greatest decrease being observed for silane).

Influence of Diatomaceous Earth Particle Size on Mechanical Properties of PLA/Diatomaceous Earth Composites.

The fractionation of diatomaceous earth (DE) using sedimentation made it possible to obtain separate unbroken diatom fractions from broken or agglomerated bodies with a range of particle sizes. The produced filler was used to prepare polylactide (PLA)/diatomaceous earth biocomposite samples containing different particle sizes, which were subjected to mechanical testing (tensile strength, flexural strength, impact strength), colloidal testing (contact angle, color change test, SEM/EDS), and thermal testing (TGA, DSC, DMA). Modification of the PLA containing the smallest particle size with diatomaceous earth (Fraction 5) resulted in a higher impact strength compared to both the pure PLA and the PLA/DE composite that contained base diatomaceous earth. Furthermore, the melt flow rate was improved by more than 80 and 60% for the composite modified with fractionated diatomaceous earth (Fraction 4) compared to pure PLA and base diatomaceous earth, respectively. The elasticity of the composite was also improved from 3.3 GPa for pure polylactide to 4.4 GPa for the system containing the smallest diatomaceous earth particles (Fraction 5).

Why POSS-Type Compounds Should Be Considered Nanomodifiers, Not Nanofillers-A Polypropylene Blends Case Study.

In this work, a series of silsesquioxanes (SSQ) and spherosilicates (SS), comprising a group of cage siloxane (CS) compounds, was tested as functional additives for preparation of isotactic polypropylene (iPP)-based nanocomposites and discussed in the aspect of their rationale of applicability as such additives. For this purpose, the compounds were prepared by condensation and olefin hydrosilylation reactions. The effect of these cage siloxane products on properties of obtained CS/iPP nanocomposites was analyzed by means of mechanical, microscopic (scanning electron microscopy-energy dispersive spectroscopy), thermal (differential scanning calorimetry, thermogravimetry), thermomechanical (Vicat softening point) analyses. The results were compared with the previous findings on CS/polyolefin composites. The role of CS compounds was discussed in terms of plastic processing additives.

Mechanical and Thermal Properties of Polylactide (PLA) Composites Modified with Mg, Fe, and Polyethylene (PE) Additives.

In this article, polylactic acid-based composites reinforced with 5% of polyethylene, iron, and magnesium powders were prepared by extrusion and compressed under the pressure of about 10 MPa and characterized. These composites were mechanically, thermally, and morphologically evaluated. It was found, compared to the pure polylactic acid (PLA), an improvement in tensile strength (both σ and YS0.2) was obtained for the composite with the iron powder addition, while the magnesium powder slightly improved the ductility of the composite material (from 2.0 to 2.5%). Degradation studies of these composites in the 0.9% saline solution over a period of 180 days revealed changes in the pH of the solution from acidic to alkaline, in all samples. The most varied mass loss was observed in the case of the PLA-5%Mg sample, where initially the sample mass increased (first 30 days) then decreased, and after 120 days, the mass increased again. In the context of degradation phenomenon of the tested materials, it turns out that the most stable is the PLA composite with the Fe addition (PLA-5%Fe), with highest tensile strength and hardness.

Silsesquioxane Derivatives as Functional Additives for Preparation of Polyethylene-Based Composites: A Case of Trisilanol Melt-Condensation.

In this work, polyethylene (PE) composites were prepared with a series of completely condensed silsesquioxanes (SSQ), as well as with open-cage hepta(isobutyl)trisilanol silsesquioxane. The effect of the additives on the thermal, mechanical, rheological, and crystalline properties of the composites obtained was determined. The dispersion of trisilanol derivative within polymer matrix was slightly better than that of the other isobutyl compounds, suggesting condensation of the additive to less polar products of different structure, which was confirmed by thermogravimetry (TG) and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry analysis. The additives improved the thermal stability of polyethylene and formed composites of higher rigidity than the neat polyolefin. The results were compared to the literature data, with aminopropylhepta(isobutyl)silsesquioxane and vinylhepta(isobutyl)silsesquioxane being used partially as references, as PE composites thereof were reported earlier, but lacked some analytical results and required further investigation. It was proven that the practical upper loading limit for such silsesquioxane compounds as processing and functional additives for polyethylene should be fixed at around 1%.

Ensembling rules in automatic analysis of pressure on plantar surface in children with pes planovalgus.

PURPOSE: This paper presents a method of ensembling rules obtained through induction of several basic types of decision trees. MATERIAL AND METHODS: The proposed method uses rules generated by means of well-known decision trees: CART, CHAID, exhaustive CHAID and C4.5. The method was tested on data describing pressure distribution under foot during gait in children with pes planovalgus (PV) and typical foot. Children with pes planovalgus underwent surgical intervention and were re-examined. Overall, 316 gait cycles have been used in analysis. RESULTS: The obtained results consist of a set of rules for all considered cases and show that the proposed method may be a useful tool of gait analysis on the basis of parameters that have a physical interpretation. CONCLUSIONS: The presented method for mining rules useful in this respect may be successfully used by persons with a typically medical knowledge and could improve the understanding of the human gait phenomenon. There is obviously no reason why this method could not be used in the case of other data as well.

TiC-composite materials in applications for kinematic denture connections.

PURPOSE: This paper presents an own proposal for the construction of a ball latch intended for use in prosthetic dentistry. Attention was paid to the existing commercial constructions of elements of the same type, indicating their advantages and disadvantages. Based on the analysis of the present solutions, own ones were proposed. MATERIALS AND METHODS: The following materials were chosen for the tests: pure titanium, 316 L V steel, Ti15Mo2.8Nb obtained using powder metallurgy and through mechanical alloying, 10 and 20% of titanium carbide - obtained using powder metallurgy, as well as 10 and 20% of graphite - obtained using powder metallurgy. For the prepared materials, tribological tests were performed using a friction simulator in a ring/shield system. RESULTS: Fairly extensive tests were performed to verify the suitability of the selected material for use in the specific conditions of the oral cavity. The performed tests showed that the proposed material is not only beneficial in relation to the existing commercial dental alloys but also meets the general criteria set for this type of elements. CONCLUSIONS: A more beneficial use of two-part ball latches (two key parts - patrix, matrix) was noticed in comparison to latches consisting of three parts (patrix, insert, matrix). On the basis of the obtained test results, it can be concluded that the proposed own design of a ball latch is a good alternative for traditional constructional and material solutions of commercial ball latches.

Improvements in self-curing composites.

PURPOSE: The purpose of this study was to test the influence of a barbituric acid derivative acting as a catalyst and small amounts of pyrolytic silica in acrylic resins on color stability, solubility and sorption of a composite. MATERIALS AND METHODS: A series of two-component powder/liquid resin systems were prepared. Monomer-like mixtures (bis-GMA, TEGDMA, tertiary amine 60/40) and a quartz powder with additions of various silica and barbituric acid derivatives were used. Temperature of the material during polymerization was measured with the use of a thermometer. In addition, the material's flexural and compressive strength, sorption and solubility were tested pursuant to ISO4049:2009. RESULTS: The powder-based acrylic composition in a liquid mixed immediately before use, after an addition of a 0.5% barbituric acid derivative, has a lower temperature during the polymerization process (a reduction from 43°C to 37°C), whereas color stability over time is improved, with ΔE=1.81 for samples of powder mixtures containing between 0.45% of BPO and 0.15% of barbituric acid derivatives. For silanized quartz powder with 0.55% BPO and 0.1% BA+0.5% Aerosil R711, the obtained sorption value was 4.57±0.22µg/mm3, whereas solubility was 1.60±0.32µg/mm3. CONCLUSIONS: New catalytic system with barbituric acid derivative, improves color stability for samples stored at room condition and under light of high intensity. A two-phase composite (bis GMA TEGDMA/Quartz), with a new catalytic system with barbituric acid derivatives, has a lower self-cured temperature. Adding a small quantity of hydrophobic silica (0.5%) has a significant influence, with reduced sorption and solubility of the material.

A device for testing the durability and exploitation reliability of dental prostheses.

PURPOSE: The aim of this work was to develop the design of the construction of a stand for testing the operational stability of dental prostheses, designed on the basis of an own idea. There are no devices that would make it possible to test complete structures, including the actual kinematics of motion and the influence of the environment of the oral cavity. MATERIALS AND METHODS: Presented were several devices used for testing both fixed and removable prostheses. Attention was paid to their limited possibilities in the area of the tested friction node, kinematics of motion, and the assessment of the influence of the environment of the oral cavity on the tested functional quality. The construction was based on the author's own ideas as well as on a review of the available literature. RESULTS: As the final result of the research, simplified images of the stand were presented along with their descriptions. CONCLUSIONS: The experimental verification of the stand allowed concluding that the research aims have been achieved. First of all, the device allows testing prosthetic structures of different sizes and it is possible to load the tested prostheses in randomly chosen points.

Occlusion trajectory and a concept of a device for testing operating life of dentures.

PURPOSE: This paper presents an original method for the assessment of occlusion trajectory. On this basis, a special device for the assessment of operating life of dentures was designed. MATERIAL/METHODS: For this purpose, the SMART system by BTS for a comprehensive movement analysis was used. In order to analyze occlusion trajectory, characteristic points on patients' heads were appointed in which markers were placed, in accordance with the rules of measurement in dentistry. Markers' movement was recorded by means of 6 cameras, and then composition of coordinates was performed in a 3D system. RESULTS: In this way, curves representing movements of the characteristic points were plotted which, after the composition, with a considerable approximation, can be regarded as occlusion trajectory. CONCLUSIONS: On the basis of the obtained results, a thesis was put forward to the effect that traditional tribological testing machines based on systems of the pin-on-disc, ball-on-disc, etc. types, due to the simplicity of their working movements, are not adequately precise for the purpose of operational assessment of elements of prosthodontics. On this basis, a tribological node for a specialist testing machine for the assessment of operating life of dentures was designed.

Influence of artificial saliva compositions on tribological characteristics of Ti-6Al-4V implant alloy.

The present paper describes the results of tests on the influence of human saliva and its substitutes on tribological characteristics of implant materials on the example of the Ti-6Al-4V (a-Ti) titanium alloy. The saliva substitutes were prepared on the basis of pyrophosphates and mucins dissolved in saline buffer. The results of the presented tribological tests show that the values of the parameters under research varied from each other, while much similarity was observed between the evaluated level of wear characteristics after the friction process in the human saliva environment and that in the environment of one of the mucins tested. The microscopic observations of surfaces of the a-Ti samples after friction revealed varied forms of tribological wear. Infrared microspectroscopy studies of surfaces of the a-Ti samples after friction revealed the presence of secondary lubricating films based on mucin found in the artificial saliva solutions.